1 definition
by
Karbowiak

The act of living vicariously though one of your own girl/boyfriends because they chose to abandon you and spend quality-time with someone else. It is widely believed "compersion" is a self-preservation technique developed by individuals that self-identify as polyamorous.

Jack has developed a keen sense of compersion to maintain his sanity after his girlfriend Jill, went to shag her other boyfriend John.